With the rapid advancements in computer networking technologies, peer-to-peer applications are becoming more and more popular. In the peer-to-peer model, any client is also a server. Peer-to-peer applications enable computer users to find each other, share files, communicate and collaborate directly for services such as chat room messaging, without the aid of dedicated network servers and services.
One of the challenges in developing peer-to-peer applications is that a peer-to-peer operation requires the cooperation of multiple computers distributed over the network, and extra development efforts are required to ensure the scalability of the application. A peer-to-peer application that scales well has a low cost (in terms of computer and network resource consumption) per additional participant in the peer-to-peer group, while the cost per additional participant of an application with poor scalability may grow rapidly to an unacceptably high level as the number of participants increases. Because peer-to-peer applications are difficult to model, it is often necessary to test them in a controlled environment on a fairly large scale to see whether they scale well. It is, however, not an easy task to properly test peer-to-peer applications, as it requires synchronizing automated test case execution across a distributed set of clients. Existing network test systems are typically unsuitable for testing peer-to-peer applications on a large scale. Many of them are designed to test applications running independently on client machines, and others are designed for testing applications running in client-server environments. Accordingly, what is needed is a new test framework that enables efficient and well-controlled testing of peer-to-peer applications on a large scale.